Document scanners are well known and are used to optically scan documents and other media in order to capture a facsimile of the object being scanned. The captured facsimile of the scanned object can then be replicated (such as in a photocopying process) or stored in a computer readable memory in the form of an image file so that the image file can be later replicated in hard-copy form, viewed on a screen, or manipulated via a computer. The optical scanning process used to capture the facsimile of the object being scanned can be an analog process, such as is commonly used in electrophotographic copying machines. More commonly, the document scanning process is a digital process, such as in the case of a “flatbed scanner”, so-called because a transparent flat platen or “bed” is used to receive and support the object being scanned during the scanning process. A flatbed scanner is typically used in conjunction with a personal computer or the like. In a digital scanning process, a light source is passed across the object being scanned, and light is reflected from the object being scanned. In an analog scanning process, the reflected light is received by an optical photoconductor (“OPC”), which can then be placed in contact with an imaging substance, such as a dry toner. The toner will be selectively attracted to or repelled from the OPC according to the exposure from the reflected light, and toner attracted to the OPC can then be transferred to imaging media such as paper or the like. In a digital optical scanning process, the light reflected from the scanned object is typically received by a charge coupled device (“CCD”) array. The CCD array provides an analog output signal representative of reflected light received from the object being scanned, and the analog output signal can then be converted to a digital signal via an analog-to-digital converter. The digital signal can then be stored in a computer readable memory for later use, as described above.
Optical document scanners typically include a housing which supports the platen, and a scan head. The platen defines an upper surface and a lower surface, and the object to be scanned is placed on the upper surface of the platen. The scan head is then configured to move across, and in proximity to, the lower surface of the platen to thereby allow the object placed on the upper surface of the platen to be scanned. The scan head typically includes a light source to illuminate the object being scanned, one or more mirrors to direct reflected light from the object being scanned to a final source (either an OPC of a CCD array), and a lens to focus the reflected light. (However, in certain configurations one or more of the mirrors, and the lens, can be placed elsewhere within the housing of the scanner, but in optical communication with the light source). The light source, mirrors, lens and final source are positioned to ensure that light reflected from the object being scanned is directed to the final source. Typically, the optical components (light source, mirrors, lens and final source) are fixed in their positions. The optical scanning process thus relies on the object to be scanned being placed on the platen in parallel orientation with the upper surface of the platen. If the object to be scanned is not parallel to the upper surface of the platen, then light from the light source will be reflected from the object at an angle other than the predetermined angle which is set to ensure that the reflected light is ultimately received by the final source. For flat objects to be scanned (such as a single sheet of paper), document scanners work very well. However, not all objects that a user desires to scan can be placed in parallel orientation to the upper surface of the platen. One particular example where this is so is in the case of a book. Frequently, a book cannot be laid on a platen so that the entirety of the pages to be scanned are in parallel orientation with the platen, or even in contact with the platen.
Turning to FIG. 1, a document scanner 10 of the prior art is depicted schematically in a side view, showing the relevant components of the scanner 10. The scanner 10 includes a housing 12 which supports a flat transparent platen 14. The platen 14 is defined by an upper surface 14U and a lower surface 14L. The scanner 10 includes a scan head 16 which is configured to be moved in direction “X” across the underside 14L of the platen 14 in order to perform the scanning process. The scan head 16 is guided by a scan head track 18, and is moved along the track by a motive means (not shown, but typically including a drive belt or cable which pulls the scan head 16 in direction “X”). The scan head 16 includes a light source 20 and a reflected light receptor 22. The reflected light receptor 22 can be a mirror, lens, or final source, as described above. The scanner 10 can also be provided with a cover 24, which is typically used to cover the object to be scanned so that during the scanning process incident light does not intrude into the platen 14, thus affecting the quality of the final scanned image. The scanner cover 24 can be supported by a flexible hinge 26 which allows the scanner cover to move upwards in direction “Z”. In this way, the scanner cover 24 allows the platen 14 to receive relatively thick objects to be scanned that would otherwise prevent the scanner cover 24 from being placed over the object if the scanner cover were simply hinged to the scanner body 12 by a simple hinge.
As depicted in FIG. 1, a book “B” has been placed on the upper surface 14U of the platen 14. The book “B” has been placed on the platen 14 so as to present pages “P1” and “P2” to the scan head 16 as the scan head moves in direction “X” across the underside 14L of the platen 14. The book “B” includes a cover “CO”, which defines a spine “S” of the book, where the pages of the book are joined to the cover “CO”. As can be seen, the spine “S” of the book “B” forces the pages “P1” and “P2” to curve upwards, away from the upper surface 14U of the platen 14 in a crease area “C”. As can also be seen, the portion of the pages “P1” and “P2” of the book “B” in the crease area “C” are not oriented in parallel arrangement to the upper surface 14U of the platen 14. Accordingly, light reflected from the portion of the pages “P1” and “P2” in the crease area “C” will likely not be reflected to the light receptor 22, resulting in loss of scanned data from the crease area “C”. Further, since the portion of the pages “P1” and “P2” in the crease area “C” are moved away from the platen 14, the illumination of the pages by the light source 20 in the crease area “C” may not be sufficient to allow a decent image to be captured. Even when there is sufficient illumination of the crease area “C” by the light source 20, and the reflected light from the crease area “C” is received by the receptor 22, the captured image in the crease area “C” will be distorted, generally resulting in compaction of the image in the crease area “C”. The problem is particularly acute for very thick books, and more so when the text on the pages to be imaged intrudes deep into the crease area “C”. Even for relatively thin books, if the cover “CO” and spine “S” are quite rigid, then text or images in the crease area “C” will not be imaged, or will be poorly imaged.
One solution to this problem is to “break” the spine “S” of the book “B” so that the book lies flatter on the platen 14. This is obviously undesirable since it will result in permanent damage to the book. Other prior solutions to this problem have been proposed, as follows.
Japanese patent JP05019371 provides for a document scanner having a wedge-shaped platen configured to receive an open book, and a scan head which moves in a rectilinear direction under the non-rectilinearly shaped platen. While this configuration accommodates the shape of an open book, it requires dual receptors to capture the reflected light from the scanned book (due to the fact that reflected light will be reflected by the book in opposite directions as the scan head crosses from the first page of the book to the adjacent second page of the book). Further, this configuration requires that light intensity from the light source be continually adjusted as the scan head moves under the book, since the distance from the pages of the book being scanned to the reflected light receptor will vary as a function of the distance from the leading edge of a page to the trailing edge of a page near the spine of the book. If no such light intensity adjustment is made, then the resulting image will not be evenly exposed, resulting in over exposure of some areas of the pages being scanned, and/or underexposure of other areas of the pages being scanned.
Japanese patent number JP2000165608 also addresses the problem of scanning an open book. The solution proposed by JP2000165608 is to provide a scanner having a two-part platen with the first and second portions arranged in a generally wedge-shape configuration to receive an open book. The scanning apparatus further requires first and second scan heads to separately scan each of the respective first and second portions of the platen. While this configuration is effective in allowing an open book to be scanned without significant loss of data in a crease area of the book, it requires complexity in the way of providing, and coordinating the operation of, two separate scan heads.
Japanese patent number JP62107569 likewise addresses the problem of scanning an open book by providing a scanner having a two-part platen with the first and second portions arranged in a generally wedge-shape configuration to receive the open book. However, in this configuration a single scan head is positioned to scan, in general parallel arrangement, only one of the two pages presented to the platen. In order to scan the second page of the open book, the book must be reoriented to allow the second page to be scanned by the single scan head. This operation requires a significant amount of user intervention, which is undesirable.
In other proposed solutions to the problem of scanning the pages of an open book, U.S. Pat. Nos. 5,475,505 and 5,712,718 provide for document scanners having a single platen which is configured to allow an open book to be placed at an extreme outside edge of the platen, thus allowing a single page of the book to be properly presented to the scan head for scanning. As with Japanese patent number JP62107569, this arrangement allows for a significant portion of the distortion and/or lost data from scanning an open book to be preserved for a single page of the open book, but again requires a user to reorient the book with respect to the platen to scan the second page of the open book.
One apparatus specifically configured for open book scanning is described in U.S. Pat. No. 4,574,316. This apparatus provides a cradle for cradling an open book in a face-up position. The cradle is adjustable to accommodate different degrees of spread between the opposing pages of the open book. An elevator moves the cradle upward so that one page of the open book is presented to a platen, and a scan head under the platen can then scan the page. In order to scan the opposing page, the cradle must be lowered and then rotated on a carousel, and then moved back in position against the platen. As can be seen, this apparatus requires a substantial number of steps to be performed to scan both pages of an open book.
Most of the prior art apparatus described above result in separate scans for each page of an open book, and thus separate printed copies for each page of the open book. However, in many instances a photocopy of both pages of an open book will fit on a single sheet of copy paper. The prior art solutions can thus substantially increase imaging media consumption.
One apparatus that allows both pages of an open book to be scanned with a single scan head is described in U.S. Pat. No. 6,313,954 B1. The apparatus described in that patent is a curved lens which is configured to be placed over the upper surface of a flatbed scanner platen. The lens is curved to receive a crease of an open book, and also to correct for distortion of the rendered image in the crease area. However, several such lenses can be necessary to accommodate different shapes of open books. Further, placing the lens on, and removing the lens from, the platen can result in the platen being scratched by the lens.